1. Field of the Invention
The disclosure relates generally to the field of magnetic disk drives, and more particularly to apparatus and methods related to testing disk drive components.
2. Description of the Prior Art
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. A typical magnetic disk drive comprises a head, including a slider and a transducer, in very close proximity to a surface of a rotatable magnetic disk. The transducer, in turn, includes a write element and/or a read element. As the magnetic disk rotates beneath the head, a very thin air bearing is formed between the surface of the magnetic disk and an air bearing surface of the slider. The air bearing causes the head to “fly” above the surface of the magnetic disk with a separation (“fly height”) that is typically less than 40 nanometers in contemporary disk drives. As the head flies over the magnetic disk, the write element and the read element can be alternately employed to write and read data bits along a magnetic “track” on the magnetic disk.
The head is positioned on the disk by a gimbaled suspension that comprises a load beam, gimbal, and swage mounting plate. Collectively, these three components and the head are frequently referred to as a Head Gimbal Assembly (HGA). The HGA is, in turn, attached to one end of an actuator arm. The other end of the actuator arm includes a winding of a conductor, called a voice coil. The actuator arm is mounted on a shaft situated between the voice coil and the load beam. In a disk drive, the voice coil is disposed between two strong permanent magnets. By adjusting the strength and the polarity of a current in the voice coil, the voice coil can be made to move between the permanent magnets. In this way the actuator arm is made to rotate around the shaft in order to control the position of the head relative to the disk to move between tracks.
Improvements in write elements have enabled increasingly higher track densities on the disk by writing tracks with increasingly more narrow track widths. Read elements have also been narrowed to match the more narrow track widths. As these dimensions have become smaller, what were once minor sources of error, such as disk run-out, have become significant obstacles to maintaining proper alignment between the head and the track. Accordingly, newer generations of disk drives are beginning to employ actuators located on the HGA in addition to the voice coil to keep the head aligned with the track. Depending on the particular location of the actuator on the HGA, these actuators are termed either milliactuators or microactuators. For example, actuators located on the swage mounting plate or load beam are typically referred to as milliactuators while actuators located on the slider or between the slider and the gimbal are typically referred to as microactuators. However, for convenience both milliactuators and microactuators will be referred to as “microactuators” for the remainder of this patent specification and the claims.
It will be appreciated that HGAs are highly complex and, accordingly, are preferably qualified before being assembled into disk drives. A spin stand is a common testing apparatus that has been developed for testing writing and reading characteristics of heads. Generally, the spin-stand includes a rotatable disk and a positioning device that secures the HGA. The positioning device allows the head to be moved to a desired position over the disk.
Accordingly, what is needed is a spin stand that is able to qualify milliactuators and micro actuators.